So I tried out both the HD800 and HD800S. The HD800S is clearly superior, in my opinion, to the HD800, if you're listening to both right out of the box. But I read that the HD800 can sound exactly like the HD800S if you properly EQ them.
So I got a trial version of Sonarworks True-Fi and tested the theory. Both headphones benefited from this software. In fact, the HD800 became superior to the HD800S (again, in my opinion). The main difference for me was that the HD800S could not reproduce the lowest notes in some of my favorite music, even with the bass cranked.
So then that got me to wondering: what could True-Fi do for the HD700, and their rather wildly erratic frequency response curve? So I bought another pair of HD700 to find out. Let me tell you, the difference was HUGE. You're exactly right: that big dip at certain frequencies is what caused my perceived loss of detail. With True-Fi restoring that detail, and taming the harshness of that bizarre peak around 6 kHz, the HD700 sound amazing! In fact, I like them better than the HD800 and HD800S! Yes, the soundstage is a little less wide, but I've surprised myself by preferring it. The 800 and 800S make everything sound like you're listening in a big echo chamber. I'm sure that's the reverb that was deliberately added in the recording studio. But the 800 and 800S make you SO aware of every detail, it gets to be almost too much. (Again, this is very much just my opinion.)
I'll be honest, I'm surprised that anyone can like the HD700 straight out of the box. It is such a unique frequency response. But, hey, we all have our preferences. I just know that the combination of HD700 and Sonarworks True-Fi provides "reference flat" frequency response in a very comfortable and affordable package. I highly recommend that everyone who likes the Sennheiser open-back sound give it a shot. Especially older guys like myself, because the Sonarworks includes the ability to compensate for age-related hearing loss. Just punch in your age and gender, and it makes the adjustment. You can then use a slider to dial in just how much of that compensation you want. It's beautiful! Music sounds like it did in my younger years again.
Thanks for your help! Your advice got me on the right track.
Interesting you picked up hd700 again. Are you still using it with mojo?
I have never used sonarworks but does it enhance feeling of being there in the audience?
Yes, classical is remarkably improved on the HD700 with Sonarworks. Without the software, some instruments were hard to hear, and others were too prominent. It was horribly unbalanced, leading to my criticism of the HD700 as being not as clear as my much cheaper HD598.
Hd700 is a soundstage depth oriented hp. Once you listen to it carefully you will realize it has more depth than any other hp, including hd800. Thats why, layer that is far away should be harder to hear. It really sounds like its coming from 10m away. I have always felt hd700 is being true to the source.
I can understand treble peak criticism, having experienced myself initially. Or even the v shaped signature, its bass sits ahead of every other instrument, and vocals, making it hard to concentrate on instruments, or giving piano a tinkly sound cause of missing mids.
But honestly, it changes as per electronics its plugged in and out of mojo + amp, all these issues for me have been resolved.